Two questions for my Lua script.

I got two questions to ask as it could help me for my "Chrono Adventure" script.

1st one:
How can I set the number of Rings lost when the player gets hurt?
Or is this even possible?

2nd one:
How can I do to make the Rings uncollectable (and transparent if possible) when the players has a certain number of Rings? ( 30 Here )
(I know I have to use if player.mo.health and blah blah, but after that?)

Don't blame me if all these things are very easy to make, I'm a newbie a Lua...

EDIT: As well, I want a bit everything like SCA.